Elly (as Jung Haerim), Yoojung, Doyeon, and Sei (as Lee Seojeong, then under LOUDers Entertainment) competed in the Mnet survival television program "Produce 101," which aired from January 22 to April 1, 2016. Yoojung and Doyeon were ranked in the final top 11 contestants and debuted in the girl group project I.O.I.

In March 2017, Weki Meki (then i-Teen Girls) opened a Naver V Live channel where 8 trainees introduced themselves to be a part of the next Fantagio girl group. These trainees were Elly, Yoojung, Doyeon, Sei, Lua, Rina, Lucy, and former trainee Yejin. On June 4 on V Live, Yoojung confirmed her place in the final line-up of Weki Meki as well as Sei, Lua, Elly. On June 5 on V Live, Doyeon confirmed her place in the final line-up as well as Lucy, Rina, and unseen trainee Ji Suyeon.

On July 6, Fantagio revealed that their new girl group would be called Weki Meki.

2017

Weki Meki released their debut extended play, WEME, on August 8, 2017. The EP contains six tracks with the lead single "I Don't Like Your Girlfriend." The album also features lyrics written by Yoojung. A month later, a limited "B Version" of their debut EP was physically released. In November, according to Gaon Music Chart, the EP sold over 47,000 physical copies since its release, making it the highest-selling album by a female idol group that debuted in 2017.

Trivia

Yoojung and Doyeon were both born in the Year of the Hare.

Lua and Rina are both Libras.

Suyeon, Yoojung, Doyeon, and Rina’s blood type is O.

Elly, Sei, and Lucy’s blood type is B.

Suyeon, Yoojung, Sei, and Lucy are from Gyeonggi-do.

Yoojung and Doyeon attended Seoul School of Performing Arts.

The shortest member, Yoojung (159 cm or 5'2½"), is shorter than the tallest member, Doyeon (170 cm or 5'7"), by 11 cm.